1. Field of the Invention
The invention relates generally to safety interlock systems for pressure vessels and particularly to such systems which are operable with mechanisms for latching a lid to a pressure vessel and for preventing release of the latching mechanism while potentially hazardous pressure conditions exist within the vessel.
1. Description of the Prior Art
Pressure vessels have long been known to be useful in a wide variety of situations, such vessels invariably including a lid which allows access to the interior of the pressure vessel. Such lids must be sealed on closure of the vessel and positively latched by a mechanism which preferably allows ready opening and closure of the lid with a minimum of effort but with a maximum of safety. A common environment in which pressure vessels are used relates to the cooking of foods under pressure, such devices typically being referred to as pressure cookers or pressure fryers. In this use environment, foods are typically cooked in oil and, under the cooking conditions, moisture in the food is released into the oil and causes relatively high pressure conditions to exist within the vessel. While these pressure conditions primarily act to cook foods within the pressure cooker, the pressure conditions also represent potentially hazardous conditions which require care to be taken in the design of the pressure cooker to prevent inadvertent and abrupt removal of the pressure cooker lid during and immediately after the cooking operation when pressure conditions within the cooker are high. Such an inadvertent opening of the pressure cooker allows immediate expansion of the moisture entrapped in the oil, the result being an explosion of the hot oil through the opening normally secured by the lid. An inadvertent and untimely opening of a pressure cooker lid in this manner thus represents a substantial hazard to an operator of the cooker. While latching mechanisms have previously been devised for maintaining the lid of a pressure cooker in place against pressure conditions existing within the cooker, the use of a safety interlock system capable of preventing inadvertent operation of the latching mechanism to open the pressure cooker has been devised in order to prevent opening of a pressure cooker while hazardous pressure conditions exist within the cooker. The safety interlock thus provides an added check to the operator's decision as to whether conditions within the cooker allow safe opening of the cooker. Such a safety interlock must be reliable and relatively incapable of being fouled and thus rendered inoperable even under the conditions encountered in a commercial cooking operation.
Stoermer, in U.S. Pat. No. 3,976,218, provides a pressure fryer safety interlock which prevents operation of a screw spindle and maintains a closure bar in sealing engagement with the lid of a pressure fryer. The Stoermer safety interlock comprises a vertically extending pin which is biased upwardly into an effective engagement with the screw spindle by pressure within the fryer acting against a lid liner, the liner biasing the pin upwardly to prevent rotation of the screw spindle. Since the channel within which the pin is held is vertically disposed with the upper end thereof being essentially open to ambient, fouling of the locking mechanism due to dripping of congealable liquids as well as dropping of solid matter such as breading and the like associated with a cooking operation provides the potential for inadequate operation of the locking structure. Failure of such a safety interlock to operate is hazardous even though the operator of the pressure cooker must primarily rely upon his own personal judgment as to the safety of proceeding with the opening of the pressure cooker.
The present invention intends improvement over the prior art including the safety interlocks previously proposed for use with pressure fryers and the like, the invention particularly providing a safety interlock system operable with a latching mechanism typically employed in a lid closure system of a pressure cooker or similar vessel to positively prevent opening of a pressure vessel lid while hazardous pressure conditions exist within the vessel. According to the present invention, the safety interlock of the present invention is configured to inhibit fouling of the mechanism by congealable liquids and solids such as breading and the like. Further, the present safety interlock is configured to maintain locking capability even during power failure. The particular structure of the present safety interlock system allows essentially continuous operation but at minimum temperature and with minimum wear such that the failure potential of the safety interlock system is minimized. Accordingly, operation of a pressure vessel such as a pressure cooker or fryer is rendered safe to a degree not heretofore realized in the art through the use of the present invention.